Laryngoscopes are used in the medical field to facilitate endotracheal intubation of a patient during surgery to provide a positive air passageway for the administration of anesthesia and/or for the mechanical ventilation of the lungs of the patient. In the human anatomy, the epiglottis normally overlies the glottis opening into the larynx to prevent the passage of food into the trachea during eating; therefore, in endotracheal intubation, it is necessary to displace the epiglottis from the glottis opening to permit the endotracheal air tube to be inserted into the trachea.
A laryngoscope having means for indirect illumination and visualization of the pharyngeal areas of the body is disclosed in my U.S. Pat. No. 4,086,919, the disclosure of which is hereby incorporated by reference. U.S. Pat. No. 4,086,919 discloses a laryngoscope (hereafter the "Bullard laryngoscope") for endotracheal intubation which comprises a housing containing a working channel for containing forceps and channels containing fiber optics for lighting and viewing the internal areas of the body; and a laryngoscope blade for manipulating the epiglottis of a patient to enable viewing of a target area.
Various other laryngoscope constructions are known. Other prior art laryngoscopes have consisted of a metal blade which is supportably attached to a handle and is inserted through the mouth of the patient into the pharyngeal area to displace the tongue and epiglottis and permit direct visualization of the glottis opening through the mouth opening. Such laryngoscopes have been provided with a light source which is directed along the blade to illuminate the area beyond the distal end of the blade Two general types of rigid blade constructions are the straight, or so called "Miller blade", and the slightly curved, or so called "Macintosh blade". Curved laryngoscope blade constructions having light means to facilitate illumination of the areas of observation are described in U.S. Pat. Nos. 3,598,113; 3,643,654; 3,766,909; and 3,771,514.
A problem exists with the other prior art laryngoscopes in that in certain situations it is not possible to visualize and access a target area such as the glottis without substantial effort and distortion of the patient's internals. The Bullard laryngoscope resolves problems in the prior art by a laryngoscope design that is simple and effective in use.
The technique of intubation utilizing Bullard laryngoscopes is accomplished with a direct view of the larynx using either an intubating forcep or a styletted endotracheal tube. The oral introduction and placement of the Bullard laryngoscope in a patient is the same whether the intubating forcep or styletted endotracheal tube is used.
The blade of the Bullard laryngoscope is inserted into the oral cavity and the laryngoscope is rotated from the horizontal to the vertical position, allowing an anatomically shaped blade to slide around the tongue. Once the laryngoscope is fully vertical, final placement is facilitated by allowing the blade to drop momentarily to the posterior pharynx of the patient. The blade is then elevated against the tongue's dorsal surface. Only minimal upward movement exerted along the axis of the laryngoscope handle is required. This upward movement will result in the blade of the Bullard laryngoscope lifting the epiglottis, providing complete visualization of the glottis opening.
Prior to insertion of the Bullard laryngoscope into the patient, the user will have loaded an endotracheal air tube onto the laryngoscope by using the jaws of the intubating forceps in the working channel of the Bullard laryngoscope to grasp a Murphy eye in the endotracheal tube. The tube is brought to the patient's laryngeal entrance together with the laryngoscope by the above steps. Thereafter, the endotracheal tube is advanced by advancing the forceps towards the vocal cords until the tube is past the obstructions in the larynx. At this point the forceps are released from the endotracheal tube and the tube may be advanced in the airway to the extent necessary.
It has been found that the physical structure of the pharynx of different patients varies, and in particular, that the location of the glottis and epiglottis is not a consistent distance from the entry of the laryngoscope at the patient's mouth. Accordingly, in some patients it is necessary to remove the laryngoscope and mount a blade tip extender thereto, and then to reinsert the laryngescope. This removal and insertion is also necessary to change the laryngoscope blade if a modular blade laryngoscope is used. ( A modular blade laryngoscope is disclosed in my U.S. Pat. No. 4,949,829, the disclosure of which is hereby incorporated by reference.) Eventually a laryngoscope with an effective blade length is obtained and the surgical procedure may continue.
It is to be appreciated that such multiple positioning and repositioning is time consuming and increases the risk of creating patient trauma and the cost of surgery. It would be desirable to minimize risk and cost by eliminating the iterative steps of determining the necessary size of a laryngoscope blade during the surgical operation.